Data processing systems often require timers in performing operations internally and performing operations with peripheral devices. These timing circuits simply indicate the passage of a specified unit of time. Traditionally, these timers, termed "watch dog timers", time single events. Upon the occurrence of the event, termed "timeout", a signal is generated or an interrupt is generated.
In the past when several timed events must be monitored, one technique requires a timer for each event. Also, software has been used to monitor clocks or timers to determine when certain time periods had expired. The disadvantage in using software is that the time required for performing individual software instructions is usually quite large compared to the resolution or increment unit of time to be measured.
It is the object of the present invention to provide a multiple event timer that provides a capability to monitor a multiple of time periods simultaneously with a single counting circuit.
A further object of the present invention is to provide the capability to designate one of several timeout conditions or signals when selected timeout conditions occur.